Introduce MeasuredEnergyStats to BatteryStatsImpl

Initial checkin that plumbs the flow of energy consumption data through
BatteryStatsService, BatteryStatsImpl, and BatteryExternalStatsWorker.

Also, start monitoring the display subsystem measured enegy consumption
and attribute energy to screen on and screen doze state.

Fixes: 171728122
Test: atest FrameworksCoreTests:MeasuredEnergyStatsTest
Change-Id: I014c2ee99da773ebc93e18d026b2e2e694d0d4b2